WHO Chapter 6

7/28/2019 WHO Chapter 6

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H ygiene in food preparation


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Basic Food Safety for H ealth W orkers

KEY POINTSl Application of general rules governing food hygiene can improve

food safety.

l WHOs Ten Golden Rules for Safe Food Preparation summarizethe most important aspects of food hygiene.

l More detailed rules are required for mass catering than fordomestic food preparation.

l Hygiene rules govern physical, operational and personal factors.

l Health workers can play an important role in educating food

handlers in food hygiene.

l General rules suffer from a lack of specificity.

l Microbiological testing of food, while specific, is ineffective

as a routine tool for assuring food safety.

l Application of procedures that are both preventive and specific such as

HACCP are the most effective way of protecting food safety.


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other organisms that might indicate thepresence of pathogens. This is a totallyunrealistic option for domestic and small-scale food preparation and, while at first

sight appealing, it has been discreditedeven for large-scale food production. I tis now almost universally recognized thatmicrobiological testing of food productson its own is an ineffective and expen-sive way of trying to achieve an accept-able level of food safety assurance.

Microbiological testing can be very costlyand only gives information after theevent, when the problem has already

arisen. I t may also give a false sense ofsecurity since microorganisms will not bespread uniformly throughout a food andsamples taken may not show the pres-ence of pathogens even though the foodis contaminated. Even when pathogensare detected, this will not necessarily in-dicate where the problem arose and howit can be solved. Without this informa-tion, the same problem is likely to recuragain and again.

A far better approach is to control micro-biological quality at source, during pro-duction or preparation, so that safety isbuilt into the product. Put simply, it ismuch better to prevent a problem fromarising than try to remedy the situationafter it has. Food hygiene rules attemptto do this but lack the specificity required.

To overcome this problem, new preventa-tive approaches have had to be devel-

oped. The most commonly implementedof these is known as the system ofHazard Analysis and Critical ControlPoint (HACCP).

HACCP involves the systematic evalua-tion of a specific food processing orpreparation procedure to identify hazardsassociated with ingredients or theprocessing procedure itself and to findout how those hazards can be control-led. It then decides which steps in theprocess are essential to controlling haz-ards so that attention can be focused onthem.

While this system was first applied tocommercial food processing, it can alsobe applied to any operation where foodis handled or processed for consumption.It is also replacing traditional regulatoryapproaches. Many countries now recog-nize HACCP in their food safety regula-tions and their enforcement proceduresare being adapted to ensure that food in-dustries apply HACCP in a systematicway.

The full rigours of a HACCP system, asoutlined in Appendix 3, are probably notfeasible or even necessary in households,but the essence of the approach identifying hazards and the key steps thatwill ensure their control is useful both atthe level of the household and moregenerally in health education campaignsand courses.


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leave the worker financially worse off asit would then be a disincentive to thehonest disclosure of any symptoms.

A person suffering from diarrhoea should

not be allowed to handle open food. Iffood is to be handled by a person withspots or infected cuts or skin lesions,these should be covered with a water-proof dressing.

It is not necessary for a food handler tohave an overt infection in order to posea threat to food safety. The asymptomaticcarriage of Staphylococcus aureuson theskin, in the nasopharynx and hair folli-

cles has already been described. Activi-ties that encourage hand/ mouth contactsuch as smoking or the chewing of gum,tobacco, betel nut or finger nails can alsotherefore lead to food contamination andmust be avoided. The same also appliesto the tasting of food during preparation.Similarly, food handlers should not spit,sneeze or cough over food, or pick theirnose, ears or any other parts of their body.

Many of the basic rules of food hygieneare already observed as part of traditionalreligious or cultural habits that go backthousands of years, but the reasons fortheir importance in terms of food safetyare often not clearly understood. It is easyfor lapses to occur resulting in a threat tofood safety. Education of food handlersin basic food hygiene is important so thatrules are not seen as pointless irritantsdreamed up by bureaucrats. If food

handlers understand the reasons for therules, this will encourage them to applythe rules rigorously and consistently. Forthe general population, basic food hygieneeducation can focus on WHOsTen goldenrulesbut more detailed training is requiredfor food handlers in mass catering. In thiseducational process, the health workercan play a significant role. This is one ofthe issues addressed in Chapter 7.

The H azard

Analysis and

Cri t ical Control

Point (H ACCP)

system

Where general rules of good foodhygiene are followed, they establish abaseline of good practice in food

preparation that can play an importantrole in ensuring food safety. The strengthof such rules lies in their generalapplicability, but this can also be a sourceof weakness. In attempting to cover allcircumstances, some rules may seemvague, or even irrelevant or unrealisticin certain situations, and to some this canappear to devalue the whole approach.Individual food preparation activities,both domestic and on a larger scale, havetheir own characteristics: they do not allproduce the same products, and they usedifferent raw materials, differentprocesses and different equipment. Whatfood handlers really want is guidance onfood safety related to their own specificoperations. Precisely how should theystore their raw materials? What are themost important areas to clean and when(sweeping a dusty floor, for instance, is

cleaning but it can actually increasecontamination of exposed food)? Howlong should the food be cooked? In whatorder should ingredients be added? Theseand many other questions are often ofgreat relevance to food safety and requirespecific answers.

One approach to checking the safety ofparticular foods would be to test them tosee if they contain specific pathogens or


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to ensure that all parts reach a tempera-ture of at least 70oC. Precooked foodsshould be stored outside the temperaturedanger zone of 1060oC and those served

hot should be reheated to 70o

C beforeconsumption.

If frozen meat and poultry are not com-pletely defrosted before cooking, someparts may not get hot enough to kill thepathogens present.

When dishes containing a mixture ofcooked and raw ingredients are beingprepared, it is important to cool thecooked component before mixing with

the other ingredients. Failure to do thiscould lead to a temporary rise in tempera-ture during which microbial growth canoccur.

The other major objective of hygienicfood handling is to avoid contamination,particularly of cooked or ready-to-eatfoods. Physical measures such as theexclusion of vermin from the premisescontribute to this, as do a number of

operational procedures such as keepingfood covered as much as possible.

The liquid that accumulates during thedefrosting of frozen meat is likely tocontain pathogenic microorganisms. Itmust not be allowed to drip on otherfoods stored below it and great care mustbe taken in disposing of it. Anyequipment or surfaces contaminatedduring defrosting must be thoroughlycleaned and disinfected.

Cooked food should be kept wellseparated from raw food to reduce therisk of cross-contamination.

Touching cooked foods with bare handsshould be avoided wherever possible aseven clean hands can carry pathogenicmicroorganisms. Ideally, hair should becovered or at the very least tied backwhen one is working in a kitchen. Hair

in food is not just aesthetically objection-able but may also be a source of patho-gens.

Personal factors:personal

hygiene and training

As indicated in Chapter 3, the foodhandler can often be a major source ofcontamination. There are several goodhygienic practices that he or she shouldobserve.

Hands should be washed regularly withsoap in clean water, but especially beforestarting to handle food, after going to thetoilet or changing a baby, and afterhandling raw food, food waste orchemicals. In all these activities the handsmay become contaminated withpathogens or toxic chemical residues thatcan then be transferred to the food. It iseasier to keep hands clean if finger nails

are kept short and jewellery such as ringsare removed as dirt can become lodgedunder these and may be difficult toremove.

Food handlers should avoid coughing intotheir hands or touching their hair, noseor mouth while handling food withoutwashing their hands afterwards.

Routine medical and microbiological ex-amination of food handlers is not gener-

ally recommended but if food handlersare suffering from an illness that includessymptoms such as jaundice, diarrhoea,vomiting, fever, sore throat, skin rash orskin lesions such as boils or cuts, theyshould report this to their supervisor be-fore starting work. It may then be neces-sary for them to be assigned temporarilyto some other task which does not in-volve handling food. This should not


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clean. In commercial food processing thisis overcome by using an antimicrobialagent (a disinfectant or sanitizer) as wellas a detergent to clean food contact sur-

faces. This can be expensive and unnec-essary at the household level. Heat is themost effective antimicrobial agent andthorough washing with hot water (morethan 80oC), perhaps with a small amountof detergent, will clean a surface and killthose microorganisms that are not easilyremoved (Figure 5.1). Frequent cleaningis also important since dried and en-crusted residues are much harder to re-move.

Cloths used for cleaning can rapidly ac-cumulate a large population of microor-ganisms, particularly when left moist, andtheir use can actually increase contami-nation rather than reduce it. They shouldtherefore be changed every day andboiled before re-use.

We have already seen how raw foods canact as a source of pathogens. I t isimportant, therefore, that the layout ofthe premises and equipment should allowfoods to be stored and handled withoutcontact between raw and cooked prod-ucts, either directly or via equipment.

The food should also be protected fromother sources of contamination such assoil, insects, rodents and other animals(wild or domesticated). For this reason,food should not be placed on or near theground in open containers. As far aspossible, the premises should beprotected to prevent pests entering. Thisis sometimes very difficult in thehousehold so storing foods in tightlysealed containers is an effective secondline of defence.

Facilities should also be available forstoring dangerous or toxic substancessuch as disinfectants and insecticidesoutside the kitchen area in a clearly

marked location. This will minimize therisk of accidents occurring as a result of

confusion between poisonous substancesand food materials. Rubbish and wasteshould also be stored away from the foodpreparation area.

The importance of not leaving food forextended periods at temperatures in thedanger zone at which microbial growthcan occur has been referred to earlier. Theequipment used to cool food is ofobvious importance here. For example,shallow trays allow faster cooling offoods and are preferable to deepercontainers. Cold storage equipmentshould be well maintained and checked

regularly to ensure it operates at thecorrect temperature. I f cold storageequipment is overloaded this will slowdown the cooling process and the foodwill spend longer in the temperaturedanger zone.

Similarly, cooking equipment should beadequate for its intended use, wellmaintained and checked regularly toconfirm that it is functioning correctly.

To allow good personal hygiene, thepremises must have adequate andhygienic toilet facilities separated fromthe food production area, as well asadequate hand-washing facilities.

Operational factors:

hygienic handling

of foodA large part of the hygienic handling offoods relates to the correct use oftemperature in the control ofmicroorganisms avoidingtemperatures where microbial growth ispossible and, where appropriate, ensuringthat temperatures are sufficiently high tokill microorganisms. For example,perishable foods should normally bestored refrigerated at


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Physical factors:

premises and

equipmentIdeally, food preparation premises shouldbe purpose built and sited in an area thatis free from objectionable odours, smokeand dust, is located away from rubbishtips, and is not prone to events such asflooding. In practice one usually has amore limited choice about the buildingto be used and its location, but it should

be of sound construction and wellmaintained.

A first requirement is that the workingenvironment should be well lit, well ven-tilated and tidy as this will encourage

good working practices and promote foodsafety. The working environment shouldalso be clean and easy to clean. Microor-ganisms can grow on any scrap or parti-cle of food remaining on food contactsurfaces or lodged in some crack or crev-ice and this can act as a source of con-tamination. While most microorganismswill be associated with food particles thatcan be removed by thorough physicalcleaning, it should be remembered that a

surface may appear physically clean al-though it may not be microbiologically

Figure 6.1 Principle components of food hygiene


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Chapter 6

Hygiene

in foodpreparation

Chapter 3 describes the principal sourcesof food contamination and these arementioned again in the discussion of thesafety of particular food commodities inChapter 4. Clearly it is important to beaware of specific problems associatedwith certain foods. However, in manycases, food safety can be enhanced by a

number of general measures, regardlessof the food materials being handled. Themost important of these have been for-mulated by WHO as a set ofTen goldenrules for safe food preparation. These are pre-sented in Appendix 2. These give guid-ance to the general population on theessential principles of safe food prepara-tion.

Though theTen golden rulesapply equallyto all food preparation activities, cateringon a larger scale is a more complexoperation than preparing food for theimmediate family and requires moredetailed rules. It involves preparing largerquantities of food for more people mainlyusing paid employees, special premises andequipment. It is also becoming increasinglyimportant as more people eat food thathas been prepared outside the home, at

work, in hospitals and educationalestablishments, at social gatherings and soon. The scale of mass catering means thatbreakdowns in good hygienic practices canhave far more serious consequences interms of the number of people affectedand, sadly, events involving mass cateringoften feature prominently in many national

statistics on outbreaks of foodborneillness. For these reasons a more extendedlist of food hygiene requirements directedat mass catering is given here. The readeris also referred to other WHO publicationsdealing specifically with this topic. (Seebibliography) Many of the rules apply tofood preparation at all levels, though someare excessive and inappropriate to foodpreparation in the home. Some instancesof this are highlighted.

Rules of good hygienic practices in foodpreparation deal broadly with three dif-ferent areas: physical factors relating tothe premises and equipment used, opera-tional factors relating to the hygienic han-dling of food, and personal factors relat-ing to questions of personal hygiene andtraining (Figure 6.1).

WHO Chapter 6

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